I though regular
oil you change it at every 3000 miles and
synthetic you change it between 7500-10000 miles ( I figure the
synthetic cost twice as much regular oild so that might be the case)
I have heard
synthetic is better
oil but not good for old car may be cause leak due to fine blend but I am not sure.
On my wife Benz, the manual stated synthetic require and change interval 7500 miles recomeded, I use regular
oil on my Porsche/BMW and change it every 3000 since its not require synthetic oil.
Oh man I am confuse and lost
TC